Pulverizer



Feb. 24, 1970 c. MILLER 3,497,143

PULVERIZER Filed July 1967 2 Sheetsl 23 MWW VENTOR. Z 54am 0, Madge E.C. MILLER PULVERIZER Feb. 24, 1970 MEL ruin n Filed July 10, 1967 UnitedStates Patent 3,497,143 PULVERIZER Earle C. Miller, Worcester, Mass.,assiguor to Riley Stoker Corporation, Worcester, Mass., a corporation ofMassachusetts Filed July 10, 1967, Ser. No. 652,140 Int. Cl. B02c 7/00,21/00; B07b 7/083 US. Cl. 24156 7 Claims ABSTRACT OF THE DISCLOSUREBACKGROUND OF THE INVENTION In the art of reducing solid fuel to a fine,burnable consistency, it has been common practice to use the socalledattrition process. For that purpose, pulverizers have been built in themanner shown in the patents of Rogers No. 3,157,366 and No. 3,235,189.As demonstrated by these patents, it is common practice first to crushthe fuel and then to cause the mixture of fuel and air to pass into apulverization chamber where air currents cause the solid particles toimpinge on one another and reduce them to a fine powder-likeconsistency. The air flow through the pulverizer is brought about by theuse of a suction fan which lies in a third chamber, the third chamberhaving an exit opening leading to the burners of a furnace or the like.Generally speaking, these fans consist of a disc mounted on the mainpulverizer rotor and have fan blades which extend axially from the discadjacent its outer periphery. This fan operates in a chamber that isfilled with comminuted fuel, some of which is fairly large in size andis later separated out in a classification apparatus and returned to thepulverizer for further comminution. This means that the fan is subjectto a considerable amount of wear. In addition, a considerable amount ofpower is required to drive the fan, and it has been suspected that partof this power was absorbed in the recirculation of air within the fanchamber to no useful purpose. These and other difiiculties experiencedwith the prior art devices have been obviated in a novel manner by thepresent invention.

It is, therefore, an outstanding object of the invention to provide apulverizer having a fan which is subject to little wear and reducedpower absorption.

Another object of this invention is the provision of a pulverizer havinga fan construction in which the fuel and air mixture is directed throughthe fan blades in such a way as to avoid direct contact with them.

A further object of the present invention is the provision of apulverizer having a fan section in which reand in which downtimenecessary for replacement of fan blades has also been reduced.

With these and other objects in view, as will be apparent to thoseskilled in the art, the invention resides in the combination of partsset forth in the specification and covered by the claims appendedhereto.

SUMMARY OF THE INVENTION Generally speaking, the pulverizer consists ofa housing having a shaft which extends through the housing and havingbearings associated with the housing for mounting the shaft forrotation. A fan mounted in the housing includes a rotor in the form of adisc which is mounted on the shaft and which extends laterally from theshaft in a generally transverse plane. Main blades extend axiallyfromthe disc adjacent its outer periphery and include a shroud joiningthe outer ends of the blades. In accordance with the invention, controlblades are fastened to the disc radially inwardly of the main blades,each control blade being arranged relative to a main blade to definetherewith a slot for direct flow through the pulverizer away from themain blades. More specifically, each main blade is provided with acontrol blade, the control blade being parallel to, slightly spacedfrom, and slightly overlapping the main blade. The invention alsoincludes a flange which extends radially from the edge of the aperturein the dividing wall of the fan chamber and which has a free edgelocated closely adjacent to the surface of the shroud to preventrecirculation of fuel and air.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention,however, may be best understood by reference to one of its structuralforms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a vertical sectional view of a pulverizer embodying theprinciples of the present invention,

FIG. 2 is a perspective view of the pulverizer as it appears to a personlooking into the interior,

FIG. 3 is a perspective view of a control blade,

FIG. 4 is a perspective view of a filler piece, and

FIG. 5 is a perspective view of a main fan blade.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, which bestshows the general features of the invention, the pulverizer, indicatedgenerally by the reference numeral 10, is shown as being of the generaltype shown and described in the patent of Rogers No. 3,235,189 whichissued Feb. 15, 1966. It is provided with a pulverization chamber 11 anda fan chamber 12. In the pulverization chamber 11 resides a main rotor13 mounted on an axial shaft 14 which, in turn, is connected to anddriven by an electric motor (not shown). The shaft is mounted inbearings 20. The outer periphery of the main rotor 13 carries movablepegs 15 which lie in suitable relationship to fixed pegs 16 mounting ona dividing wall 17. This dividing wall extends between the chamber 11and the chamber 12 and is provided with a central aperture 18 which isco-axial with the shaft 14. Mounted in the aperture 18 is a ring 19having a tubular flange 21 whose purpose will be described more fullyhereinafter.

In the fan chamber 12 is locaed a disc 22 which is mounted on the shaft14 and is driven also with the shaft by the electric motor. Adjacent itsouter periphery, the disc is provided with main fan blades 23 whichextend axially in the direction of the dividing wall 17. Mounted on theends of the main fan blades parallel to the disc 22 but spaced from itis a shroud 24. This shroud is simply a circular plate having anaperture 25 formed in its central portion concentric with the shaft 14.The extreme end of the flange 21 lies closely adjacent the surface ofthe shroud 24 at the periphery of the aperture 25.

Mounted on the disc 22 inwardly of the main fan blades 23 are controlblades 26, one control blade being associated with each main blade 23.Each controlblade 26 is mounted parallel to, spaced from, and inslightly overlapping relationship to its corresponding main blade 23.Welded to the inner surface of the shroud 24 in overlapping relationshipwith the free end of each control blade 26 is a metal sealing strip 27.

Referring to FIG. 5, it can be seen that each of the main fan blades 23consists of a generally rectangular main body 28. Along one side of themain body is a flange 29 by which it is bolted to the disc 22 and alongthe opposite edge is a flange 31 for attachment of the shroud. Referringto FIG. 3, it can be seen that each control blade 26 has a plate-likemain body 32 along one edge of which extends a flange 33 by which it isbolted to the disc 22. Opposite the flange 33 the main body has a radialedge 34 which is the edge that lies closely adjacent the inner surfaceof the shroud 24 and which edge is in overlapping relationship to thesealing strip 27. The main body is also provided with an inclined edge35 which, in the preferred embodiment lies at an angle of about 45 tothe axis of the shaft 14. Both the main blades 23 and the control blades26 are provided with raised ridges to promote breaking up of theboundary layer of air flowing over their surfaces.

In FIG. 4 can be seen a filler 38 which is shaped similar to the flanges29 and 33 and extends between them to prevent there being any gap in theflanges between the control blade and the main blade. Finally, it can beseen that the wall of the fan chamber 12 is provided with an exit 36which leads to the furnace burners and the like.

The operation of the invention will now be readily understood, in viewof the above description. Most of all, the general flow of air throughthe pulverizer is between the movable pegs 15 and the fixed pegs 16 inthe pulverizing chamber 11 radially inwardly toward the aperture 18 inthe dividing wall. A mixture of air and fuel flows through this aperturearound the flange 21 through the aperture 25 and the shroud 24 andstarts to move radially outwardly as well as axially. As is evident inFIG. 2, the gap 37 between the control blade 26 and the main blade 23acts as a nozzle and, with the fan rotating in the direction shown bythe arrow in FIG. 2, the fuel and air between the fan blades will moveradially outwardly and desirably would reach the outer periphery of thefan housing before contacting the next blade 23. Finally, the flow willenter the exit 36 and leave the fan chamber.

In prior art pulverizers, there was a tendency for the flow to also flowfrom the outer periphery of the main blades 23 back inwardly along thesurface of the dividing wall 17 to enter the flow coming in through thoeaperture 18 again, thus passing through the pulverizer more than once.Since it takes horsepower on the shaft 14 to promote this type ofrecirculation flow, considerable losses were experienced for thatreason. With the present construction, the flange 21 lying close to theouter surface of the shroud 24 near the aperture 25 prevents suchrecirculation. Possible bypassing of air around the outer edge 34 of thecontrol blade 26 has been obviated by the use of the sealing strip 27.

In a commercial installation of the pulverizer of the invention, the fanefliciency has been increased about by use of the present constructionrather than that of the prior art as shown in the above-mentioned Rogerspatent. This has reduced the pulverizer input power for the sameperformance level by approximately 20 kw. In other words, the powerconsumption on the motor driving the pulverizer has been reduced by thisamount. At a cost of .6 per kw. for electricity and operation of thepulverizer for 8,000 hours per year, this would result in a saving ofalmost $2,000 for the four pulverizers of a conventional central stationsteam generating unit. The maintenance of the new fan assembly wassubstantially less than that of the old types and there have been feweroutages or shutting down of the pulverizer for the replacement-offanblades.

It it obvious that minor changes may be made in the form andconstruction of the invention without departing from the material spiritthereof. It is not, however, desired to confine the invention to theexact form herein shown and described, but it is desired to include allsuch as properly come within the scope claimed.

The invention having been thus described, what is claimed as new anddesired to secure by Letters Patent is:

1. A pulverizer, comprising (a) a housing,

(b) a shaft extending through the housing,

(c) bearings associated with the housing for mounting the shaft forrotation,

(d) a fan mounted in the housing, including a rotor in the form of adisc mounted on the shaft and extending laterally from the shaft in agenerally transverse plane, including main blades extending axially fromthe disc adjacent its outer periphery, and including a shroud joiningthe outer ends of the blades, and

(e) control blades fastened to the disc radially inwardly of the mainblades, each control blade being arranged relative to a main blade todefine a slot to direct flow through the pulverized away from the mainblades.

2. A pulverizer as recited in claim 1, wherein each main blade has acontrol blade associated with it, the control blade being parallel to,slightly spaced from, and slightly overlapping the main blade.

3. A pulverizer as recited in claim 1, wherein a dividing wall extendsacross the housing and has a central aperture through which the shaftextends, the diameter of the aperture being substantially larger thanthe shaft to define an air passage around the shaft, wherein a flangeextends axially from the edge of the aperture and has a free edgelocated closely adjacent to the surface of the shroud.

4. A pulverizer as recited in claim 1, wherein the edge of the controlblade which is not fastened to the disc lies closely adjacent the shroudand wherein a seal strip is mounted on the shroud and located close tothe surface of the control blade to maintain the gap between the bladeand the shroud to a minimum.

5. A pulverizer as recited in claim 1, wherein each main blade and itscorresponding control blade are provided with flanges by which they arefastened to the discs, the flanges being of different widths so that theedges of the flanges are aligned even though the blades do not lie inthe same plane, and wherein a filler is interposed between the twoflanges to provide an uninterrupted radial strip fastened to the surfaceof the disc.

6. A pulverizer as recited in claim 3, wherein each control blade isprovided with an inner edge which is inclined at an acute angle to theaxis of the shaft.

7. A pulverizer, comprising (a) a housing,

(b) a shaft extending through the housing,

(c) bearings associated with the housing for mounting the shaft forrotation,

(d) a fan mounted in the housing, including a rotor in the form of adisc mounted on the shaft and extending laterally from the shaft in agenerally transverse plane and including blades extending axially fromthe disc adjacent its outer periphery,

(e) a dividing wall extending across said housing defining a chamber forsaid fan and having a central aperture through which said shaft extends,the diameter of said aperture being substantially larger than said shaftto define an air passage around said shaft,

(f) a shroud joining the outer ends of said blades,

and

(g) a sealing member between said dividing wall and 6 said shroudwhereby circulation of the air from 3,157,366 11/1964 Rogers 241-188said outer periphery of said fan to said central 3,235,189 2/1966 Rogers241188 aperture is substantially prevented.

FOREIGN PATENTS References Cited 5 287,278 7/1931 Ita1y. UNITED STATESPATENTS 201,347 3/1878 Hyatt 241 55 ROBERT C. RIORDON, Primary Examiner2,361,278 10/1944 Evans 24156 2 330 773 4 1953 Reich g D. G. KELLY,Assistant Examiner

